The present invention relates to a headrest including an inflatable protective cushion activated in the case of a rear-end impact.
In a rear-end impact a vehicle occupant is exposed to added risk of injury in the region of the nape of the neck due to shear and bending forces when the head is not in contact with the headrest. This is, however, mostly the case since the vehicle occupant when on the move often shifts to a more comfortable seating position which is not always an optimum from the safety point of view. To reduce this risk of injury headrests have been developed with which by means of an inflatable protective cushion the contact surface area of the upholstery of the headrest is increased whilst being caused to approach the head. So that a movement of the headrest upholstery is possible, known headrests are provided with either an elastic covering material or seams in the covering material which burst on inflation of the protective cushion to thus deploy a folded portion of the cover and thereby permit expansion of the protective cushion. This results in the cover being irreversibly damaged once the protective cushion has been deployed. Apart from this, providing these burst seams constitutes an additional, not inconsiderable complication in fabricating the headrest. When employing an elastic covering material the choice of material is substantially restricted due to the required elastic properties which affects the costs and freedom in visual design of the headrest.
The present invention provides a headrest including an inflatable protective cushion in which the contact surface area is increased and caused to approach the head without needing to provide burst seams in the upholstery or in the cover or to make use of an elastic covering material.
The protective cushion is arranged between the headrest frame member and the upholstery. The cover or the upholstery is joined at its outer circumference by jointing means to the headrest frame member. The jointing means maintain the cover, or the upholstery, tensioned in the non-activated condition of the protective cushion and permit a limited displacement of the outer circumference of the cover, or upholstery, from the headrest frame member in the activated condition of the protective cushion. Thus, the upholstery may be brought by the protective cushion nearer to the head and the contact surface area may be enlarged without destroying the cover or upholstery. The upholstery and/or the cover may be returned to their original positions after having been activated.
Furthermore, the invention provides an activating means which on detection of a rear-end impact activates a gas source for inflating the protective cushion, the activating means comprising a pressure sensor responding to the pressure exerted by the occupant on the backrest of the vehicle seat, and an acceleration sensor applied to the vehicle body or to the seat and which activates the gas source only when pressure is exerted by the occupant on the backrest and simultaneously the acceleration sensor signals a rear-end impact. It is this activating means that prevents the protective cushion in the headrest from being inflated when despite pressure being exerted on the backrest no rear-end impact is involved or when the corresponding vehicle seat is not occupied.